Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$165.35	10.125%	$182.0917	$182.09	$182.10	$182.10
Purchase #2	$229.40	4.715%	$240.2162	$240.22	$240.20	$240.20
Purchase #3	$244.64	4.783%	$256.3411	$256.34	$256.35	$256.30
Purchase #4	$132.74	5.300%	$139.7752	$139.78	$139.80	$139.80
Purchase #5	$72.48	11.604%	$80.8906	$80.89	$80.90	$80.90
Purchase #6	$89.77	4.759%	$94.0422	$94.04	$94.05	$94.00
Purchase #7	$22.60	9.606%	$24.771	$24.77	$24.75	$24.80
7 purchase totals =	$956.98		$1,018.1280	$1,018.13	$1,018.15	$1,018.10